In the industry field, a contactor is a common electrical apparatus, which can control turn-on/off of main-voltage/current supply through a lower voltage/current control signal. The contactor is applied widely in the industry field and can control electrical loads such as an electrical motor, an illumination apparatus, a heat supply apparatus, and a capacitor bank. In the applications, a function of the contactor is generally turning on or off a load power source line repeatedly.
The contactor generally includes either a Normal Open (NO) type or a Normal Close (NC) type contact system. A basic structure of the contactor is described in the following with reference to an NO-type contactor. The NO-type contactor may generally include a contact portion and an actuation portion. The contact portion is a portion in the contactor for bearing a load current, which is generally made of low-resistance metal (for example, copper or silver), and generally includes a static contact and a moving contact. When the static contact contacts the moving contact (the two contacts are closed), the load current is turned on, and when the static contact and the moving contact are disconnected from each other, the load current is turned off.
As the name implies, in the NO-type contactor, the static contact and the moving contact are kept in a disconnection state by using gravity or a spring force in a initial normal state; while the static contact and the moving contact of the contact portion are in a closed state in the switched-to non-normal state. After being actuated by electrical energy, the actuation portion can provide a required driving force, so that the contact portion is closed and the closed state is kept.
The NC-type contactor has a structure similar to that of the NO-type contactor. The difference is only that, in the NC-type contactor, the static contact and the moving contact are generally in the closed state in an initial state, and after being actuated, the actuation portion provides a driving force so that the static contact and the moving contact of the contact portion are disconnected from each other.
In the industry field, the most common contactor is an electromagnetic contactor, which controls opening and closing of the contactor through electromagnetic actuation. Documents 1 to 3, listed below, describe the electromagnetic contactor separately.
A basic operating principle of the electromagnetic contactor is described in the following with reference to FIG. 1. An electromagnetic contactor 1 is an NO-type contactor and includes a pair of static contacts 103 and 104, a pair of moving contacts 101 and 102, an electromagnet 106, an armature 105, a coil 108, and a spring 107. When a current is switched on for the coil 108, the armature 105 made of a magnetic material and the electromagnet 106 are actuated to have magnetism of opposite polarities. The armature 105 is opposite to the electromagnet 106 and is connected to the pair of moving contacts 101 and 102.
When the armature 105 and the electromagnet 106 have the magnetism, the armature 105 moves towards the electromagnet 106 and compresses the spring 107 under the action of an attractive force of the electromagnet 106. At this time, the moving contacts 101 and 102 move towards the static contacts 103 and 104 and contact the static contacts 103 and 104 respectively under driving of the armature 105, so that electrical energy flows through the contact portions to be provided to a load, thereby forming a load current. When the actuation current in the coil 108 is turned off, the magnetism of the armature 105 and electromagnet 106 disappears, the armature 105 moves away from the electromagnet 106 under action of an elastic restoring force of the spring 107, and the moving contacts 101 and 102 are disconnected from the static contacts 103 and 104 respectively under driving of the armature 105, so the load current is turned off.
In the foregoing description, when the current is switched on for the coil, the armature and the electromagnet attract each other due to opposite magnetic poles, but in a contactor with a different structure, an armature may also be made of a special material such as an anti-magnetic material, so that when a current is switched on for a coil, the armature and the electromagnet have the same magnetic poles and repel each other.
It can be seen from the foregoing embodiment that, according to the operating principle of the NO-type electromagnetic contactor, for the purpose of enabling the moving contact to move towards the static contact, the current needs to flow through the coil to magnetize the electromagnet, thereby generating an enough attractive force for attracting the armature. Meanwhile, if the closed state of the contactor needs to be kept, the current flowing through the coil needs to be kept to continuously provide the magnetism of the electromagnet and the attractive force for attracting the armature.
In other words, during a static period in which the NO-type electromagnetic contactor keeps the closed state, electrical energy consumption always exists in the coil of the contactor. The NC-type electromagnetic contactor has the similar situation. Especially, for example, in some industry applications such as electrical motors, energy consumed by the electromagnetic contactor during the static period is considerable.
Document 1: U.S. Pat. No. 4,616,202A
Document 2: U.S. patent application NO. US2010/0308944A1
Document 3: PCT patent application NO. WO2011/021329A1